b
(b)Let two boys meet at point \(C\) after time \('t'\) from the starting.

Then \(AC = v\,t\), \(BC = {v_1}t\)\({(AC)^2} = {(AB)^2} + {(BC)^2}\)

\(⇒\) \({v^2}{t^2} = {a^2} + v_1^2{t^2}\)

By solving we get \(t = \sqrt {\frac{{{a^2}}}{{{v^2} - v_1^2}}} \)